Design of non-foster circuits realized by transistors and operational amplifiers

• Main Author: Mo, Tao
• Other Authors: Tan Eng Leong
• Format: Thesis-Master by Coursework
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Electrical and electronic engineering
• Online Access: https://hdl.handle.net/10356/169498
• Institution: Nanyang Technological University

This report explores the use of a negative impedance converter to create a non-Foster circuit for matching small antennas. This approach overcomes the limitations of passive matching, such as low efficiency and narrow bandwidth, and facilitates wideband and miniaturized antenna design. The study focuses on the properties and applications of non-Foster components, covering the following aspects: This report involves the design and analysis of grounded and floating non-Foster circuits made with transistors. A SP (S-Parameter) model is established to determine the negative impedance conversion coefficient for the grounded non-Foster circuit. Another PB (packaged BJT) model is created, and the circuit is connected in parallel or in series with the equivalent circuit of the small antenna to offset its virtual reactance. The circuit's stability is analyzed by analyzing the poles of its transfer function, confirming its stability within the frequency band of the study. This report involves the design and analysis of a non-Foster circuit using an operational amplifier. The study begins with the design of a grounded non-Foster circuit with an operational amplifier. Next, the circuit is connected in parallel with the equivalent circuit model of a small antenna, resulting in effective matching within the 20MHz-40MHz frequency range. The stability of the circuit is also analyzed through the poles of its transfer function.